Synthesis and structure-activity relationships of novel fused ring analogues of Q203 as antitubercular agents

Article abstract of DOI:10.1016/j.ejmech.2017.05.021

A set of fused ring analogues of a new antitubercular agent, Q203, was designed and synthesized. To reduce the lipophilicity of Q203 caused by linearly extended side chains, shorter and heteroatoms containing fused rings were introduced into the side chain region. Antitubercular activity was tested against H37Rv-GFP replicating in liquid broth culture medium (extracellular) and within macrophages (intracellular). Many analogues showed potent extracellular activities as well as intracellular activities without cytotoxicity. Among them, compounds 18–21 displayed significant antitubercular activities with favorable metabolic stabilities. Representative compound 21 exhibited excellent in?vivo pharmacokinetic values at high drug exposure levels in the plasma, which makes this compound promising candidate for a new antitubercular drug.

Full text of DOI:10.1016/j.ejmech.2017.05.021

Accepted Manuscript
Synthesis and structure-activity relationships of novel fused ring analogues of Q203
as antitubercular agents
Sunhee Kang, Young Mi Kim, Heekyung Jeon, Sejin Park, Min Jung Seo, Saeyeon
Lee, Dongsik Park, Jiyeon Nam, Seokwoo Lee, Kiyean Nam, Sanghee Kim,
Jaeseung Kim
PII:
S0223-5234(17)30382-3
10.1016/j.ejmech.2017.05.021
EJMECH 9451
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 16 March 2017
Revised Date: 4 May 2017
Accepted Date: 5 May 2017
Please cite this article as: S. Kang, Y.M. Kim, H. Jeon, S. Park, M.J. Seo, S. Lee, D. Park, J. Nam, S.
Lee, K. Nam, S. Kim, J. Kim, Synthesis and structure-activity relationships of novel fused ring analogues
of Q203 as antitubercular agents, European Journal of Medicinal Chemistry (2017), doi: 10.1016/
j.ejmech.2017.05.021.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

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Synthesis and structure-activity relationships of novel fused ring analogues of Q203 as antitubercular
agents
Sunhee Kang,1,3 Young Mi Kim,1 Heekyung Jeon,1 Sejin Park,1 Min Jung Seo,1 Saeyeon Lee,1 Dong
sik Park,1 Jiyeon Nam,1 Seokwoo Lee,3 Kiyean Nam,2 Sanghee Kim,3,* and Jaeseung Kim1,*
1Chemistry Platform, Institut Pasteur Korea, 16 Daewangpangyo-ro, 712 Beon-gil, Bundang-gu, Seong
2
nam-si, Gyeonggi-do, 13488, Republic of Korea; Qurient Co. Ltd., 242 Pangyo-ro, Bundang-gu, Seo
3
ngnam-si, Gyeonggi-do, 13488, Republic of Korea; College of Pharmacy, Seoul National University,
1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
ABSTRACT
A set of fused ring analogues of a new antitubercular agent, Q203, was designed and synthesized.
To reduce the lipophilicity of Q203 caused by linearly extended side chains, shorter and heteroatoms
containing fused rings were introduced into the side chain region. Antitubercular activity was tested
against H37Rv-GFP replicating in liquid broth culture medium (extracellular) and within macrophage
s (intracellular). Many analogues showed potent extracellular activities as well as intracellular activiti
es without cytotoxicity. Among them, compounds 18-21 displayed significant antitubercular activities

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with favorable metabolic stabilities. Representative compound 21 exhibited excellent in vivo pharmac
okinetic values at high drug exposure levels in the plasma, which makes this compound promising
candidate for a new antitubercular drug.
Keywords
Tuberculosis, imidazo[1,2-a]pyridine-3-carboxamide (IPA), pharmacokinetics (PK), structure-activity
relationship (SAR), Q203
1. Introduction
Tuberculosis (TB) is an infectious disease with a high worldwide mortality. Overall, an estimated 2–3
billion people have been infected with TB, including 5–15% latent infections that will develop an active
infection in their lifetime.1 The current standard regimen involves a combination of the drugs, isoniazid
(INH), rifampicin (RIF), pyrazinamide (PZA), and ethambutol (EMB) for 6 months for the treatment of
drug-susceptible TB. However, the treatment period may be extended up to 24 months as well as there are
limited number of effective drugs for multidrug resistant (MDR) and extensive drug resistant (XDR) TB
patients.2–3 Research during the last decade has led to the development of two new drugs, bedaquiline and
delamanid (Figure 1), for the treatment of drug resistant TB patients.4–7 According to the latest reports,1 there
are nine antitubercular drugs in the clinical development stage including some already approved and

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repurposed drugs. However, new chemical entities that have novel mode of action are still not sufficient to
overcome the emerging resistance to the current drugs, and therefore discovery of new drug candidates is
required.
Q203 (Figure 1) is an imidazo[1,2-a]pyridine-3-carboxamide (IPA) analogue, that we developed to treat
drug resistant TB, and it is one of new compounds in current clinical trials. It has novel mode of action, in
that inhibits ATP production by targeting cytochrome bc1 complex within M. tuberculosis.8 Based on the
structure of Q203, we have tried to find other clinical candidates that have comparable potency as well as in
vivo pharmacokinetic values. According to our previous studies of structure-activity relationship (SAR), the
imidazo[1,2,a]pyridine carboxamide is critical for the antitubercular activity. In addition, extended long side
chain led to superior potency and lipophilicity of the side chain was more important than linearity8-10. In this
study, we designed new IPA analogues possess a fused aromatic ring on the side chain region. The study was
initially aimed to reduce size of the side chain and logP value caused by extended long side chain of Q203
and our efforts led to another promising drug candidate that having comparable potency and in vivo
pharmacokinetic properties with Q203.

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Figure 1. Structure of bedaquiline, delamanid and Q203
2. Result and discussion
2.1.
Synthesis of fused ring IPA analogues
The designed IPAs (4-21) were synthesized by a EDC-mediated coupling reaction between imidazo[1,2-
a]pyridine carboxylic acid and corresponding benzylamines and the synthesis of imidazo[1,2-a]pyridine
carboxylic acid was followed our previously published methods (Scheme 1).9,10,11 Briefly, the required
imidazo[1,2-a]pyridine carboxylic acids (3a and 3b) were prepared via bromination of ethyl 3-oxopentanoate
using N-bromosuccinimide (NBS), followed by condensation with 5-chloro or 4-chloroamino pyridine at a
reflux temperature, and then saponification. Benzylamine counterparts for the preparation of target
carboxamides listed in Table 1 were obtained from commercial sources or synthesized from commercially
available benzonitriles by lithium aluminum hydride (LAH).9 Self-prepared benzylamines used to produce
target carboxamides are listed in Table 2, and their synthesis is described in Scheme 2. A
cyclohexanecarboxylic acid (22) was activated by oxalyl chloride and then coupled with 3-amino-4-

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hydroxybenzonitrile (25). Cyclization in the presence of pyridinium p-toluene sulfonate at a refluxed
temperature proceeded to get target benzonitrile (23).12 Compound 26 was prepared from 25 with 2-chloro-
1,1,1-trimethoxyethane by heating, and then morpholine was introduced using a SN2 reaction to synthesize
the nitrile intermediate 27. Similarly to the synthesis of 23, benzonitriles 33 and 34 were prepared from
benzoic acid 29 and 30, respectively, via coupling with 25 and cyclization. The synthesized nitrile
intermediates were subsequently converted to benzylamines by LAH or nickel borohyride reduction13 (24,
28, 35, and 36).
Scheme 1. Synthetic scheme of imidazo[1,2-a]pyridine-3-carboxamidesa
aReagents and conditions: (i) NBS, NH4OAc (over 2.0 eq.), Et2O, rt, 6 h; (ii) 5-chloro or 4-chloroamino
pyridine, EtOH, reflux, overnight; (iii) LiOH, EtOH/H2O (3:1, v/v), rt, overnight; (iv) counterpart
benzylamine, EDC, HOBt, TEA, DMF, 80°C, 2–4 h
Scheme 2. Synthetic scheme of 2-substituted benzo[d]oxazole-5-ylmethanaminea

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aReagents and conditions: (i) oxalyl chloride, CHCl3, rt, 1 h; (ii) 25, 1,4-dioxane, reflux, overnight; (iii)
.
pyridinium p-toluene sulfonate, xylene, reflux, overnight; (iv) NaBH4, NiCl2 6H2O, EtOH, 0°C, rt, 1 h; (v) 2-
chloro-1,1,1-trimethoxyethane, EtOH, reflux, 5 h; (vi) morpholine, DMF, rt, overnight; (vii) thionyl chloride,
25, CH2Cl2, rt, 1 h; (viii) LAH, THF, reflux, 3 h
2.2. Structure-activity relationship (SAR) study
The activity of the fused ring IPA derivatives was evaluated with H37Rv-GFP that was replicating in liquid
broth culture medium (extracellular MIC80), and was also evaluated inside macrophages (intracellular
MIC80).8,14 In addition, metabolic stability was tested in rodent and human liver microsomal preparations to
select compounds for in vivo pharmacokinetic evaluation (Table 1 and Table 2). In subsequent SAR studies,
the R1 substituents were fixed with the 6-chloro or 7-chloro group for all IPA analogues because they
showed good antitubercular activity and exhibited favorable metabolic stability in our previous study.9 Our
initial aim was focused on finding compounds having reduced lipophilicity than Q203 by introducing simple

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fused rings on the side chain region. To assist in lipophilicity of designed molecules and Q203, AlogP
prediction derived from Discovery Studio (2016, BIOVIA, San Diego, CA) was employed.
Table 1 summarizes the SARs of a set of compounds that had a fused ring moiety as the side chain. The
structures of the side chains of all designed compounds were shorter and simpler compared to Q203 that had
an extended lipophilic side chain. Therefore, our calculation indicated that all designed compounds have
lower ALogP values (2.19 ~ 4.31) than Q203 (7.88). The study began with naphthyl group as R2 to examine
a simple hydrophobic side chain effect. The results showed that compounds 4 and 5 exhibited the desired
extracellular activity (MIC80 of 0.0315 µM and 0.125 µM, respectively) and intracellular activity (MIC80 of
0.062 µM and 1.00 µM, respectively) without an extended lipophilic side chain. However, they were
extensively metabolized in human and rat liver microsomes. With a promising antitubercular activity as
comparable small fused ring analogues, we introduced heteroatoms containing fused heterocycles as a side
chain (6-13) to find compounds that had potent antitubercular activity with favorable metabolic stability.
Benzo[d]oxazole analogues 6 and 7 showed approximately 6- and 12-fold decreased extracellular activity
with reduced lipophilicity, respectively, but showed similar activities against M. tuberculosis replicating
inside macrophages when compared with compounds 4 and 5. In addition, metabolic stability in human liver
microsomes was considerably improved, although they still showed extensive metabolism in rat liver
microsomes. When the indole moiety (8–10) was introduced, N-methylated analogues 9 and 10 showed
better potency than compound 8 (extracellular MIC80 values of 0.50 µM and 0.031 µM, respectively) and the
position of nitrogen was more favorable when placed in the para direction from the benzylic linker, as shown

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in Q203. Further studies also showed that benzo[d][1,3]dioxole analogue 11 displayed excellent potency
against M. tuberculosis replicating in the liquid broth culture medium (extracellular MIC80 value of 0.082
µM) and also excellent potency inside macrophages (intracellular MIC80 value of 0.009 µM). However, all
indole and benzo[d][1,3]dioxole-containing analogues showed extensive metabolism in both human and rat
liver microsomes. Additionally, benzo[b][1,4]oxazin-3-one and benzimidazole were introduced as side
chains, but they did not show any antitubercular activities. Overall, from SARs of the simple fused ring
analogues, we found several compounds that had nano molar range of MIC values, but it was difficult to
obtain favorable in vitro metabolic stabilities.
We therefore designed and synthesized an additional set of benzo[d]oxazole-containing analogues because
compound 6 and 7 showed better metabolic stability among the small fused ring analogues listed in Table 1.
We postulated that these analogues could be a good starting point to make derivatives for improvement of
antitubercular activity and metabolic stability. Our previous studies showed that an extended side chain
conferred improved potency,9 so we introduced cyclohexyl, methyl morpholine, and substituted phenyl
groups instead of a methyl group at position 2 of benzo[d]oxazole (14–21). The antitubercular activity and
metabolic stability are summarized in Table 2. Compounds 14 and 15 with a cyclohexyl at position 2 of
benzo[d]oxazole showed improved extracellular activity with an MIC80 value of 0.082 µM for both
compounds. However, they were metabolically unstable, and the ALogP increased to 5.31 after introducing
the cycloalkyl group. Compounds 16 and 17 with polar methyl morpholine were designed to reduce the
ALogP value, but this led to an approximate 10-fold decrease in antitubercular activity (extracellular MIC80

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values of 2.67 µM and 13.7 µM, respectively) compared to compounds 6 and 7. Notably, analogues 18 and
19 with a 4-fluorophenyl group at position 2 of the benzo[d]oxazole showed potent activity and improved
microsomal stability compared to compounds 14 and 15. Based on these results, 4-trifluoromethoxyphenyl
was introduced at position 2, because general metabolic stability was followed in order of trifluoromethoxy >
chlorine > fluorine from our previous study.9 As a results, compounds 20 displayed excellent potency with
extracellular and intracellular MIC values of 0.027 µM and 0.009 µM, respectively. Moreover, metabolic
stability was significantly improved in human and rat microsomes. Compound 21 containing 7-Cl as R1 was
the most potent in extracellular and intracellular activity evaluations (0.009 µM and <0.001 µM,
respectively) with good metabolic stability among the listed analogues. In our SAR study for fused ring
analogues described in Table 1 and Table 2, increased lipophilicity affected the antitubercular activity, and a
6-chloro substituent on the R1 position resulted in better potency than the 7-chloro analogue. Whereas, the 7-
chloro group on R1 had better metabolic stability than the 6-chloro derivatives and the instability of the 2-
methyl benzo[d]oxazole analogues in human and mouse microsomes was improved by substitution of
phenyl ring at 2-position instead of methyl group.
Table 1. Activity and metabolic stability of fused ring IPA analogs against M. tuberculosis H37Rva,b,c

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aExtracellular MIC80 = the inhibitory activity against M. tuberculosis H37Rv replicating in culture broth
b
medium; intracellular MIC80 = the inhibitory activity against M. tuberculosis H37Rv replicating inside
macrophages; MIC80 is the minimum concentration required to inhibit growth by 80% and indicates an
c
average value of two independent measurements. antitubercular activity of Q203 were adapted from
reference 9.

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Table 2. Activity and metabolic stability of benzoxazole analogues against M. tuberculosis H37Rva
aAnti-tubercular activity of Q203 was adapted from reference 9.
2.3. In vivo pharmacokinetic (PK) evaluation
Based on the promising antitubercular activity and metabolic stability, we selected compound 21 for in vivo
pharmacokinetic (PK) evaluations. The experiment was performed in mice after intravenous and oral
administration of 2 and 10 mg/kg, respectively. As shown in Table 3, compound 21 reached a maximum
concentration within 1h, displayed a long half-life (t1/2, 36.3 h) from low systemic clearance and it
resulted to high drug exposure levels (AUC0-inf, 116400 ng.h/mL) after oral administration. Although 40%
bioavailability was arithmetically lower than 90% of Q203 but it doesn’t actually mean lower bioavailability

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than Q203 because it showed much higher drug exposure level (AUC0-inf) in the plasma with longer half-life
(t1/2) than Q203 and exhibited high drug concentration even at 24h (supporting information, Figure S1).
Table 3. In vivo pharmacokinetic values of compound 21 in micea
aThe PK values for compound Q203 were taken from reference 8 and presented for comparison.
3. Conclusion
In summary, a series of fused ring IPA analogues were designed and synthesized and their antitubercular
activities were evaluated. Linearly extended side chain of Q203 was replaced with a set of shorter fused
ring moieties to reduce length of the side chain and logP values. All synthesized analogues showed reduced
AlogP values compared to Q203 as well as some of them displayed good antitubercular activities without
long side chain. In addition, low metabolic stability was successfully improved by introducing substitution
at 2-position from simple benzo[d]oxazoles. Our representative compound 21 exhibited superior potency
against H37Rv-GFP replicating inside macrophage with MIC values of below 1 nM that is more potent than
Q203 with recuced Alog P value. In our in vivo studies, compound 21 exhibited excellent orally available

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pharmacokinetic properties (PK) with high drug exposure level and long half-life. This compound could
therefore be a promising antitubercular candidate which has comparable potency and ADME properties
with Q203 and additional in vivo efficacy study will be reported in due course.
4. Experimental
4.1. Chemistry
All reactions were carried out under an argon atmosphere in oven-dried glassware with magnetic
stirring and the reaction solvents were purified by passage through a bed of activated alumina.
Purification of reaction products was carried out by flash chromatography using silica gel 60 (Merck,
230-400 mesh). Analytical thin layer chromatography was performed on 0.25 mm silica gel 60-F254
plates (Merck). Visualization was accomplished with 254 nm of UV light and PMA or potassium
permanganate staining followed by heating. Melting points (mp) were measured on an electro thermal
melting point apparatus, M-565 (BÜCHI). 1H-NMR (at 400 MHz) and 13C-NMR (at 100 MHz) spectra
were reported on a Varian 400 MHz spectrometer. 1H-NMR spectra (CDCl3 at 7.26 ppm) and 13C-NMR
spectra (CDCl3 at 77.2 ppm) were recorded in ppm using solvent as an internal standard. Data are
reported as (ap = apparent, s = singlet, d= doublet, t = triplet, q = quartet, m = multiplet, br = broad;
coupling constant(s) in Hz; integration). LC/MS data were obtained using a Waters 2695 LC and
Micromass ZQ spectrometer. The purity of all biologically tested compounds was ≥95 % by HPLC.

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Yields refer to purified products and are not optimized. The concentration determination (extracellular
& intracellular) and in vivo pharmacokinetics were performed as previously described.8, 14
4.1.1. General Procedure for Preparation of acid counterpart 4-21.
The synthesis of ethyl 2-bromo-3-oxopentanoate (2) and imidazo[1,2-a]pyridine-3-carboxylic acid
(3a-b) was synthesized according to published methods in reference 9. Benzylamine counterparts for
the preparation of compounds 4-13 were purchased from commercial source or synthesized from
commercially available benzonitrile by LAH and detailed procedure is described below (reduction of
benzonitrile, method B).
4.1.1.1.
Synthesis of 6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxylic acid (3a). White solid; mp =
178-179 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.25 (t, J = 7.6 Hz, 3H), 3.02 (q, J = 7.6 Hz, 2H), 7.57
13
(dd, J = 9.2, 2.0 Hz, 1H), 7.71 – 7.74 (m, 1H), 9.32 – 9.33 (m, 1H), 13.31 (brs, 1H); C NMR (100
MHz, DMSO-d6) δ 13.74, 23.01, 112.74, 117.82, 125.90, 128.79, 145.05, 157.79, 162.43; LCMS
(ESI) m/z 225 [M + H]+.
4.1.1.2.
Synthesis of 7-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxylic acid (3b). White solid; mp =
158-159 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.24 (t, J = 7.6 Hz, 3H), 3.02 (q, J = 7.6 Hz, 2H), 7.18
13
(dd, J = 7.6, 2.4 Hz, 1H), 7.83 (d, J = 2.4 Hz, 1H), 9.26 (d, J = 7.6 Hz, 1H); C NMR (100 MHz,
DMSO-d6) δ 13.77, 22.97, 112.86, 115.06, 115.79, 115.83, 129.16, 132.95, 146.36, 157.75, 162.51;
LCMS (ESI) m/z 225 [M + H]+.

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4.1.2. General Procedure for Preparation of benzylamines (24, 28, 35 and 36)
4.1.2.1. Synthesis of 2-cyclohexylbenzo[d]oxazole-5-carbonitrile (23)
To a stirred solution of cyclohexylcarboxylic acid (3.8 mmol) in CHCl3 (15 mL) was treated oxalyl
chloride (11.4 mmol) and the mixture was stirred for an hour at room temperature. The solvent was
evaporated under reduced pressure then the resulting residue was dissolved in 1,4-dioxane (20 mL). 3-
Amino-4-hydroxybenzonitrile (4.2 mmol) was added and the reaction mixture was refluxed for
overnight. Again, the organic solvent was evaporated. Xylene (20 mL) and pyridinium p-toluene
sulfonate (4.2 mmol) were added and the reaction mixture was refluxed for overnight. After reaction
completion, the mixture was diluted with EtOAc and washed with water and brine. The organic phase
was dried over MgSO4 and concentrated in vacuo. The crude residue was washed with n-hexane to give
1
benzonitrile intermediate 23. White solid; H NMR (400 MHz, CDCl3) δ 1.37 – 1.48 (m, 3H), 1.64 –
1.77 (m, 3H), 1.84 – 1.89 (m, 2H), 2.14 – 2.18 (m, 2H), 2.95 – 3.00 (m, 1H), 7.54 – 7.60 (m, 2H), 7.98
(d, J = 0.8 Hz, 1H); LCMS (ESI) m/z 227 [M + H]+.
4.1.2.2. Synthesis of 2-(Chloromethyl)benzo[d]oxazole-5-carbonitrile (26)
A mixture of 3-amino-4-hydroxybenzonitrile (2.98 mmol) and 2-chloro-1,1,1-trimethoxyethane (3.28
mmol) in ethanol (15 mL) was stirred and refluxed for 5h. The reaction mixture was cooled to room
temperature then evaporated. Cold diethyl ether was poured to the crude residue and the generating
insoluble solid was filtered off. The resulting filtrate was concentrated and the crude residue was

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purified by flash column chromatography (n-hexane:EtOAc = 5:1 ratio) to give compound 26 (86%,
1
white solid). H NMR (400 MHz, CDCl3) δ 4.77 (s, 2H), 7.66 – 7.71 (m, 2H), 8.08 – 8.01 (m, 1H);
LCMS (ESI) m/z 193 [M + H]+.
4.1.2.3. Synthesis of 2-(morpholinomethyl)benzo[d]oxazole-5-carbonitrile (27)
To a stirred solution of compound 26 (1.04 mmol) in N,N-dimethylformamide (4 mL) was added
morpholine (1mL) and the reaction mixture was stirred for overnight at room temperature. The mixture
was concentrated and the crude residue was purified by flash column chromatography (n-hexane:EtOAc
= 3:2 ratio) to give compound 27 (71%, white solid). 1H NMR (400 MHz, CDCl3) δ 2.64 – 2.67 (m, 4H),
3.76 – 3.78 (m, 4H), 3.89 (s, 2H), 7.62 – 7.67 (m, 2H), 8.04 (d, J = 0.8 Hz, 1H); LCMS (ESI) m/z 244
[M + H]+.
4.1.2.4. Synthesis of 2-(4-trifluoromethoxy)benzo[d]oxazole-5-carbonitrile (34)
To a stirred solution of 4-trifluoromethoxybenzoic acid (4.4 mmol) in dry methylene chloride (5 mL)
was added thionyl chloride (5.5 mmol) slowly and the mixture was stirred for an hour. The mixture was
concentrated and the residue was dissolved in 1,4-dioxane (10 mL). 3-Amino-4-hydroxybenzonitrile (3.7
mmol) was added and the reaction mixture was stirred at refluxed temperature for overnight. Again, the
mixture was concentrated. Xylene (10 mL) and pyridinium p-toluene sulfonate (4.4 mmol) were added
and the reaction mixture was refluxed for overnight. After reaction completion, the mixture was diluted
with EtOAc and washed with water and brine. The organic phase was dried over MgSO4 and

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concentrated in vacuo. The crude residue was purified by recrystallization with diethyl ether to give
compound 34 (88%, white solid). 1H NMR (400 MHz, DMSO-d6) δ 7.61 (d, J = 8.8 Hz, 2H), 7.90 (dd, J
= 8.0, 0.8 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 8.31 – 8.33 (m, 2H), 8.40 – 8.41 (m, 1H); LCMS (ESI) m/z
305 [M + H]+.
In a similar manner, the compound 33 was synthesized according to this procedure.
4.1.2.5. Reduction of benzonitriles to give compounds 24, 28, 35 and 36
Method A (For 24 and 28): To a stirred solution of benzonitrile (0.69 mmol) and nickel chloride
hexahydrate (1.05 mmol) in ethanol (20 mL) was added sodium borohydride (2.10 mmol) under ice-bath.
The reaction was allowed to room temperature and further stirred for 1.5 h. Water (5 mL) was added to
the mixture and stirred for 5 min. The resulting insoluble black residue was filtered off using cellite and
washed with methylene chloride. The filtrate was concentrated to give crude product and it was used for
next reaction without further purification.
Method B (For 35 and 36): To a stirred solution of benzonitrile (0.43 mmol) in tetrahydrofuran (5 mL)
was added lithium aluminum hydride (1.30 mmol) and the mixture was refluxed for 3h. The reaction
was quenched with 1N aqueous NaOH under ice-bath and insoluble residue was filtered off using cellite.
The resulting filtrate was extracted with EtOAc (2 times), washed with brine, dried over MgSO4 and
concentrated in vacuo. The crude product was used for next reaction without further purification.
4.1.3. Synthesis of target imidazo[1,2-a]pyridine-3-carboxamides (4-21).

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To a stirred solution of 6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxylic acid (3a or 3b, 2.83
mmol) in anhydrous DMF (10 mL) was added 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride (3.84 mmol), 1-hydroxybenzotriazole (1.54 mmol), triethylamine (5.12 mmol) and
corresponding benzylamines (2.56 mmol) at room temperature, then the resulting solution was heated to
70℃ with stirring. After 2 hours, the reaction mixture was cooled to room temperature and evaporated.
Water (50 mL) was added into the crude residue, the resulting solid was collected by filtration, the filter
cake was washed with water (50 mL) and dried to afford crude product. The resulting crude compound
was purified by flash column chromatography (n-hexane:EtOAc:methylene chloride = 1:1:1), then
recrystallized from EtOAc to give target compound, 4-21.
6-Chloro-2-ethyl-N-(naphthalen-2-ylmethyl)imidazo[1,2-a]pyridine-3-carboxamide (4). White solid; mp
= 194-195 ℃; 1H NMR (400 MHz, CDCl3) δ 1.40 (t, J = 7.6 Hz, 3H), 2.98 (q, J = 7.6 Hz, 2H), 4.87 (d,
J = 5.6 Hz, 2H), 6.19 (brs, 1H), 7.29 – 7.32 (m, 1H), 7.47 – 7.56 (m, 4H), 7.82 – 7.88 (m, 4H), 9.56 –
13
9.57 (m, 1H); C NMR (100 MHz, DMSO-d6) δ 13.58, 22.38, 43.07, 116.23, 117.64, 120.14, 125.38,
125.95, 126.12, 126.37, 126.65, 127.56, 127.99, 128.40, 132.56, 133.35, 137.43, 143.81, 151.64, 161.10;
LCMS (ESI) m/z 364 [M + H]+; HRESIMS calcd for C21H18ClN3O [M + H]+ 364.1211, found
364.1227.
7-Chloro-2-ethyl-N-(naphthalen-2-ylmethyl)imidazo[1,2-a]pyridine-3-carboxamide (5). White solid; mp
= 181-182 ℃; 1H NMR (400 MHz, MeOH-d4) δ 1.32 (t, J = 7.6 Hz, 3H), 3.02 (q, J = 7.6 Hz, 2H), 4.78
(s, 2H), 7.06 (dd, J = 6.8, 1.6 Hz, 1H), 7.44 – 7.59 (m, 4H), 7.82 – 7.87 (m, 4H), 8.96 (d, J = 7.6 Hz,

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1H); 13C NMR (100 MHz, DMSO-d6) δ 13.62, 22.34, 43.06, 114.34, 115.59, 116.03, 125.94, 126.12,
126.37, 126.65, 127.98, 128.39, 128.57, 131.88, 132.56, 133.35, 137.47, 145.25, 151.58, 161.11; LCMS
(ESI) m/z 364 [M + H]+; HRESIMS calcd for C21H18ClN3O [M + H]+ 364.1211, found 364.1237.
6-Chloro-2-ethyl-N-((2-methylbenzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-carboxamide (6).
1
White solid; mp = 172-173 ℃; H NMR (400 MHz, CDCl3) δ 1.39 (t, J = 7.6 Hz, 3H), 2.64 (s, 3H),
2.97 (q, J = 7.6 Hz, 2H), 4.78 (d, J = 5.6 Hz, 2H), 6.15 (brs, J = 5.6 Hz, 1H), 7.31 -7.35 (m, 2H), 7.46 (d,
J = 8.4 Hz, 1H), 7.55 (d, J = 9.2 Hz, 1H), 7.65 (s, 1H), 9.54 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ
13.54, 14.59, 22.34, 42.86, 110.48, 116.19, 117.63, 118.29, 120.14, 124.55, 125.33, 127.55, 136.17,
141.70, 143.78, 149.88, 151.58, 161.02, 164.75; LCMS (ESI) m/z 369 [M + H]+; HRESIMS calcd for
C19H16ClN4O2 [M + H]+ 369.1113, found 369.1124.
7-Chloro-2-ethyl-N-((2-methylbenzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-carboxamide (7).
1
White solid; mp = 245-246 ℃; H NMR (400 MHz, CDCl3) δ 1.38 (t, J = 7.6 Hz, 3H), 2.64 (s, 3H),
2.96 (q, J = 7.6 Hz, 2H), 4.77 (d, J = 6.0 Hz, 2H), 6.14 (brt, J = 6.0 Hz, 1H), 6.90 (dd, J = 7.6, 2.4 Hz,
1H), 7.31 (dd, J = 8.4, 2.0 Hz, 1H), 7.45 (d, J = 8.4 Hz, 1H), 7.60 (d, J = 2.4 Hz, 1H), 7.65 (d, J = 2.0 Hz,
1H), 9.36 (d, J = 7.6 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 13.58, 14.58, 22.31, 42.86, 110.47,
114.35, 115.59, 115.99, 118.29, 124.54, 128.54, 131.88, 136.21, 141.70, 145.23, 149.88, 151.53, 161.02,
164.75; LCMS (ESI) m/z 369 [M + H]+; HRESIMS calcd for C19H16ClN4O2 [M + H]+ 369.1113,
found 369.1124.

ACCEPTED MANUSCRIPT
N-((1H-indol-6-yl)methyl)-6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxamide (8). Pale yellow
solid; mp = 123-124 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.26 (t, J = 7.6 Hz, 3H), 2.99 (q, J = 7.6 Hz,
2H), 4.61 (d, J = 6.0 Hz, 2H), 6.37 – 6.39 (m, 1H), 7.03 (dd, J = 8.0, 1.2 Hz, 1H), 7.29 – 7.31 (m, 1H),
7.39 (s, 1H), 7.45 (dd, J = 9.2, 2.0 Hz, 1H), 7.50 (d, J = 8.0 Hz, 1H), 7.67 (d, J = 9.2 Hz, 1H), 8.48 –
13
8.49 (m, 1H), 9.08 (d, J = 2.0 Hz, 1H), 11.03 (s, 1H); C NMR (100 MHz, DMSO-d6) δ 13.55, 22.31,
43.40, 101.28, 110.72, 116.36, 117.65, 119.37, 120.12, 120.27, 125.24, 125.70, 127.05, 127.44, 132.47,
136.42, 143.72, 151.42, 160.88; LCMS (ESI) m/z 353 [M + H]+; HRESIMS calcd for C19H17ClN4O
[M + H]+ 353.1164, found 353.1171.
6-Chloro-2-ethyl-N-((1-methyl-1H-indol-6-yl)methyl)imidazo[1,2-a]pyridine-3-carboxamide (9). White
solid; mp = 149-150 ℃; 1H NMR (400 MHz, CDCl3) δ 1.36 (t, J = 7.6 Hz, 3H), 2.95 (q, J = 7.6 Hz, 2H),
3.80 (s, 3H), 4.82 (d, J = 5.6 Hz, 2H), 6.13 (brs, 1H), 6.49 (d, J = 3.2 Hz, 1H), 7.08 (d, J = 2.8 Hz, 1H),
7.12 (dd, J = 8.0, 1.2 Hz, 1H), 7.30 (dd, J = 9.6, 2.0 Hz, 1H), 7.34 (s, 1H), 7.55 (d, J = 9.6 Hz, 1H), 7.63
13
(d, J = 8.0 Hz, 1H), 9.54 (d, J = 1.2 Hz, 1H); C NMR (100 MHz, DMSO-d6) δ 13.62, 22.31, 32.80,
43.47, 100.56, 108.90, 116.43, 117.65, 119.41, 120.08, 120.68, 125.25, 127.50, 130.14, 132.69, 136.84,
143.69, 151.43, 160.88; LCMS (ESI) m/z 367 [M + H]+; HRESIMS calcd for C20H19ClN4O [M + H]+
367.1320, found 367.1338.
6-Chloro-2-ethyl-N-((1-methyl-1H-indol-5-yl)methyl)imidazo[1,2-a]pyridine-3-carboxamide
(10).
White solid; mp = 201-202 ℃; 1H NMR (400 MHz, CDCl3) δ 1.37 (t, J = 7.6 Hz, 3H), 2.94 (q, J = 7.6
Hz, 2H), 3.81 (s, 3H), 4.78 (d, J = 5.6 Hz, 2H), 6.07 (m, 1H), 6.48 (d, J = 3.2 Hz, 1H), 7.09 (d, J = 2.8

ACCEPTED MANUSCRIPT
Hz, 1H), 7.24 – 7.26 (m, 1H), 7.29 (dd, J = 9.6, 2.0 Hz, 1H), 7.34 (d, J = 8.4 Hz, 1H), 7.53 (d, J = 9.6 Hz,
1H), 7.63 (s, 1H), 9.54 (d, J = 1.2 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 13.55, 22.29, 32.94, 43.34,
100.59, 109.99, 116.40, 117.63, 119.68, 120.07, 121.56, 125.24, 127.41, 128.39, 130.16, 130.34, 136.06,
143.69, 151.38, 160.82; LCMS (ESI) m/z 367 [M + H]+; HRESIMS calcd for C20H19ClN4O [M + H]+
367.1320, found 367.1333.
N-(benzo[d][1,3]dioxol-5-ylmethyl)-6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxamide (11). White
solid; mp = 179-180 ℃; 1H NMR (400 MHz, CDCl3) δ 1.31 (t, J = 7.6 Hz, 3H), 2.90 (q, J = 7.6 Hz, 2H),
4.51 (d, J = 5.6 Hz, 2H), 5.89 (s, 2H), 6.38 (brs, 1H), 6.71 – 6.80 (m, 3H), 7.23 (dd, J = 9.6, 2.0 Hz, 1H),
13
7.43 (d, J = 9.6 Hz, 1H), 9.34 (d, J = 2.0 Hz, 1H); C NMR (100 MHz, CDCl3) δ 13.27, 23.21, 43.50,
101.24, 108.32, 108.52, 116.63, 121.11, 121.70, 126.10, 128.48, 131.86, 144.35, 147.20, 148.12, 151.31,
161.15; LCMS (ESI) m/z 358 [M + H]+; HRESIMS calcd C18H16ClN3O3 [M + H]+ 358.0953, found
358.0967.
6-Chloro-2-ethyl-N-((3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)methyl)imidazo[1,2-a]pyridine-3-
carboxamide (12). White solid; mp = 228-229 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.26 (t, J = 7.6 Hz,
3H), 2.50 (q, J = 7.6 Hz, 2H), 4.42 (d, J = 6.0 Hz, 2H), 4.53 (s, 2H), 6.90 – 6.92 (m, 3H), 7.09 (dd, J =
7.2, 2.0 Hz, 1H), 7.78 (d, J = 2.0 Hz, 1H), 8.44 (brt, J = 6.0 Hz, 1H), 8.96 (d, J = 7.6 Hz, 1H), 10.71 (s,
1H); 13C NMR (100 MHz, DMSO-d6) δ 13.51, 22.29, 42.33, 67.20, 114.32, 115.27, 115.59, 115.96,
116.38, 122.45, 127.56, 128.52, 131.87, 134.15, 142.56, 145.22, 151.51, 160.98, 165.42; LCMS (ESI)
m/z 385 [M + H]+; HRESIMS calcd C19H17ClN4O3 [M + H]+ 385.1062, found 386.0906.

ACCEPTED MANUSCRIPT
N-((1H-benzo[d]imidazol-6-yl)methyl)-6-chloro-2-ethylimidazo[1,2-a]pyridine-3-carboxamide
(13).
Pale yellow solid; mp = 245-246 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.25 (t, J = 7.6 Hz, 3H), 2.98 (q,
J = 7.6 Hz, 2H), 4.63 (d, J = 5.6 Hz, 2H), 7.09 (dd, J = 7.6, 2.0 Hz, 1H), 7.23 (d, J = 8.0 Hz, 1H), 7.54 –
7.57 (m, 2H), 7.78 (d, J = 2.0 Hz, 1H), 8.18 (s, 1H), 8.50 (brt, J = 5.6 Hz, 1H), 8.96 (d, J = 7.6 Hz, 1H),
13
12.39 (s, 1H); C NMR (100 MHz, DMSO-d6) δ 13.58, 22.30, 43.23, 114.30, 115.58, 115.61, 116.10,
122.05, 128.48, 131.81, 133.50, 142.59, 145.17, 151.42, 160.94; LCMS (ESI) m/z 354 [M + H]+;
HRESIMS calcd C18H16ClN5O [M + H]+ 354.1116, found 354.1115.
6-Chloro-N-((2-cyclohexylbenzo[d]oxazol-5-yl)methyl)-2-ethylimidazo[1,2-a]pyridine-3-carboxamide
(14). White solid; mp = 167-168 ℃; 1H NMR (400 MHz, CDCl3) δ 1.30 – 1.44 (m, 6H), 1.59 – 1.74 (m,
3H), 1.84 – 1.88 (m, 2H), 2.14 – 2.17 (m, 2H), 2.96 (q, J = 7.6 Hz, 3H), 4.78 (d, J = 5.6 Hz, 2H), 6.19
(brs, 1H), 7.28 (d, J = 1.6 Hz, 1H), 7.30 – 7.34 (m, 1H), 7.46 (d, J = 8.0 Hz, 1H), 7.53 (d, J = 9.2 Hz,
13
1H), 7.67 (s, 1H), 9.53 (d, J = 2.4 Hz, 1H); C NMR (100 MHz, CDCl3) δ 13.07, 21.15, 22.55, 25.57,
30.44, 37.93, 43.81, 110.56, 113.96, 116.47, 117.78, 119.09, 124.31, 124.67, 125.92, 126.47, 132.37,
133.93, 141.72, 150.10, 158.95, 171.14; LCMS (ESI) m/z 437 [M + H]+; HRESIMS calcd for
C24H25ClN4O2 [M + H]+ 436.1666, found 436.1677.
7-Chloro-N-((2-cyclohexylbenzo[d]oxazol-5-yl)methyl)-2-ethylimidazo[1,2-a]pyridine-3-carboxamide
(15). White solid; mp = 154-155 ℃; 1H NMR (400 MHz, CDCl3) δ 1.25 – 1.46 (m, 6H), 1.60 – 1.73 (m,
3H), 1.84 – 1.87 (m, 2H), 2.13 – 2.17 (m, 2H), 2.92 – 2.97 (m, 3H), 4.77 (d, J = 5.6 Hz, 2H), 6.12 (brs,
1H), 6.89 (d, J = 7.2 Hz, 1H), 7.31 (d, J = 8.0 Hz, 1H), 7.46 (d, J = 8.0 Hz, 1H), 7.58 (s, 1H), 7.67 (s,

ACCEPTED MANUSCRIPT
1H), 9.36 (d, J = 7.2 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ 13.56, 22.31, 25.32, 25.74, 30.38,
37.28, 42.93, 110.63, 114.33, 115.59, 115.97, 118.61, 124.64, 128.55, 131.87, 136.20, 141.40, 145.23,
149.52, 151.53, 161.03, 170.57; LCMS (ESI) m/z 437 [M + H]+; HRESIMS calcd for C24H25ClN4O2 [M
+ H]+ 436.1666, found 436.1684.
6-Chloro-2-ethyl-N-((2-(morpholinomethyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-
carboxamide (16). Pale yellow solid; mp = 92-93 ℃; 1H NMR (400 MHz, CDCl3) δ 1.37 (t, J = 7.6 Hz,
3H), 2.62 - 2.64 (m, 4H), 2.94 (q, J = 7.6 Hz, 2H), 3.74 -3.76 (m, 4H), 3.85 (s, 2H), 4.78 (d, J = 5.6 Hz,
2H), 6.18 (brt, J = 5.6 Hz, 1H), 7.28 (dd, J = 9.6, 2.0 Hz, 1H), 7.37 (dd, J = 8.0, 1.2 Hz, 1H), 7.51 -7.54
13
(m, 2H), 7.70 (d, J = 1.2 Hz, 1H), 9.51 (d, J = 2.0 Hz, 1H); C NMR (100 MHz, DMSO-d6) δ 13.53,
22.35, 42.88, 53.19, 54.99, 66.52, 110.97, 116.16, 117.63, 118.88, 120.15, 125.27, 125.36, 127.56,
136.49, 141.08, 143.80, 149.81, 151.60, 161.04, 163.95; LCMS (ESI) m/z 454 [M + H]+; HRESIMS
calcd for C23H24ClN5O3 [M + H]+ 453.1568, found 453.1579.
7-Chloro-2-ethyl-N-((2-(morpholinomethyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-
1
carboxamide (17). White solid; mp = 200-201 ℃; H NMR (400 MHz, CDCl3) δ 1.37 (t, J = 7.6 Hz,
3H), 2.63 -2.65 (m, 4H), 2.94 (q, J = 7.6 Hz, 2H), 3.75 -3.77 (m, 4H), 3.86 (s, 2H), 4.79 (d, J = 6.0 Hz,
2H), 6.13 (brt, J = 6.0 Hz, 1H), 6.90 (dd, J = 7.2, 2.0 Hz, 1H), 7.37 (dd, J = 8.4, 1.6 Hz, 1H), 7.52 (d, J =
8.4 Hz, 1H), 7.59 (d, J = 2.0 Hz, 1H), 7.72 (d, J = 1.6 Hz, 1H), 9.36 (d, J = 7.2 Hz, 1H); 13C NMR (100
MHz, DMSO-d6) δ 13.58, 22.32, 42.88, 53.19, 54.98, 66.52, 110.95, 114.35, 115.59, 115.95, 118.88,

ACCEPTED MANUSCRIPT
125.26, 128.56, 131.89, 136.53, 141.08, 145.24, 149.79, 151.56, 161.05, 163.94; LCMS (ESI) m/z 454
[M + H]+; HRESIMS calcd for C23H24ClN5O3 [M + H]+ 453.1568, found 453.1578.
6-Chloro-2-ethyl-N-((2-(4-fluorophenyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-
carboxamide (18). White solid; mp = 258-259 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.25 (t, J = 7. 6 Hz,
3H), 2.99 (q, J = 7.6 Hz, 2H), 4.65 (d, J = 5.6 Hz, 2H), 7.41 – 7.46 (m, 4H), 7.64 (d, J = 9.6 Hz, 1H),
7.74 (d, J = 8.4 Hz, 1H), 7.78 (s, 1H), 8.21 – 8.25 (m, 2H), 8.54 (t, J = 5.6 Hz, 1H), 9.08 (d, J = 2.0 Hz,
1H); 13C NMR (100 MHz, DMSO-d6) δ 13.52, 22.38, 42.91, 111.08, 116.15, 116.90, 117.12, 117.63,
118.97, 120.15, 123.52, 123.55, 125.38, 125.58, 127.56, 130.30, 130.39, 137.01, 142.05, 143.81, 149.79,
151.63, 161.09, 162.30, 163.43, 165.93; LCMS (ESI) m/z 449 [M + H]+; HRESIMS calcd for
C24H18ClFN4O2 [M + H]+ 448.1102, found 448.1107.
7-Chloro-2-ethyl-N-((2-(4-fluorophenyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-a]pyridine-3-
carboxamide (19). White solid; mp = 261-262 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.25 (t, J = 7. 2 Hz,
3H), 2.98 (q, J = 7.2 Hz, 2H), 4.64 (d, J = 5.6 Hz, 2H), 7.07 (d, J = 7.6 Hz, 1H), 7.42 – 7.46 (m, 3H),
7.75 (d, J = 8.4 Hz, 2H), 7.77 (s, 1H), 8.23 (d, J = 8.4 Hz, 2H), 8.55 (brs, 1H), 8.96 (d, J = 7.2 Hz, 1H);
13C NMR (100 MHz, DMSO-d6) δ 13.58, 22.34, 42.90, 111.09, 114.37, 115.59, 115.96, 116.92, 117.14,
118.97, 125.58, 128.58, 130.32, 130.41, 131.90, 137.06, 142.05, 145.26, 149.79, 151.59, 161.10, 162.38,
163.4, 165.9; LCMS (ESI) m/z 449 [M + H]+; HRESIMS calcd for C24H18ClFN4O2 [M + H]+ 448.1102,
found 448.1108.

ACCEPTED MANUSCRIPT
6-Chloro-2-ethyl-N-((2-(4-(trifluoromethoxy)phenyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-
a]pyridine-3-carboxamide (20). White solid; mp = 239-240 ℃; 1H NMR (400 MHz, CDCl3) δ 1.40 (t, J
= 7.6 Hz, 3H), 2.99 (q, J = 7.6 Hz, 2H), 4.82 (d, J = 6.0 Hz, 2H), 6.20 (brs, 1H), 7.31 (dd, J = 7.6, 1.6 Hz,
1H), 7.35 (d, J = 8.4 Hz, 2H), 7.42 (dd, J = 8.4, 1.6 Hz, 1H), 7.55 (d, J = 9.2 Hz, 1H), 7.59 (d, J = 8.4 Hz,
1H), 7.77 (s, 1H), 8.29 (d, J = 8.8 Hz, 2H), 9.55 (d, J = 1.6 Hz, 1H); 13C NMR (100 MHz, DMSO-d6) δ
13.53, 22.38, 42.90, 111.22, 116.20, 117.63, 119.14, 120.15, 122.11, 125.38, 125.89, 126.02, 127.58,
130.00, 137.15, 141.98, 143.82, 149.86, 151.08, 151.64, 161.10, 161.93; LCMS (ESI) m/z 515 [M +
H]+; HRESIMS calcd for C25H18ClF3N4O3 [M + H]+ 514.1020, found 514.1023.
7-Chloro-2-ethyl-N-((2-(4-(trifluoromethoxy)phenyl)benzo[d]oxazol-5-yl)methyl)imidazo[1,2-
a]pyridine-3-carboxamide (21). White solid; mp = 244-245 ℃; 1H NMR (400 MHz, DMSO-d6) δ 1.27
(t, J = 7.2 Hz, 3H), 3.00 (q, J = 7.2 Hz, 2H), 4.66 (d, J = 6.0 Hz, 2H), 7.10 (dd, J = 8.0 Hz, 2.4 Hz, 1H),
7.48 – 7.50 (m, 1H), 7.61 (d, J = 8.4 Hz, 2H), 7.77 – 7.81 (m, 3H), 8.32 (d, J = 8.4 Hz, 2H), 8.56 (t, J =
13
6.0 Hz, 1H), 8.98 (d, J = 7.6 Hz, 1H); C NMR (100 MHz, DMSO-d6) δ 13.58, 22.34, 42.90, 111.21,
114.37, 115.60, 115.95, 119.13, 122.12, 125.88, 126.02, 128.59, 129.99, 131.92, 137.19, 141.98, 145.26,
149.86, 151.00, 151.60, 161.10, 161.93; LCMS (ESI) m/z 515 [M + H]+; HRESIMS calcd for
C25H18ClF3N4O3 [M + H]+ 514.1020, found 514.1025.
ASSOCIATED CONTENT

ACCEPTED MANUSCRIPT
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
AUTHOR INFORMATION
Corresponding Author
*Jaeseung Kim (Jaeseung K.); Phone: +82-31-8060-1603, Fax.: +82-31-8060-1649, E-mail:
silanediol@gmail.com;
*Sanghee Kim (Sanghee K.); Phone: +82-31-880-2487, E-mail: pennkim@snu.ac.kr
Author Contributions
H.J. performed the growth inhibition experiments, Sunhee K., Y.M.K., M.J.S., S.L., D.P., Sanghee K. and
J.K. designed and synthesized the compounds, J.N. evaluated the in vitro metabolic stability, S.P. performed
the in vivo efficacy studies, Y.M.K. analyzed the purity of the compounds, Seokwoo L. calculated ALogP,
K.N. designed and performed the in vivo PK evaluations, and Sunhee K. wrote the manuscript with
contributions from the other authors. Sanghee K. and Jaeseung K. supervised the synthesis of the molecules,
and J.K. supervised the TB project.
Acknowledgements

ACCEPTED MANUSCRIPT
This work was supported by the National Research foundation of Korea (NRF) grant funded by the Korean
government (MSIP) (NRF-2014K1A4A7A01074643), and Gyeonggi-do and Qurient Co. Ltd.
Abbreviation
TB, tuberculosis; MDR, multidrug-resistance; XDR, extensive drug-resistance; EDC, 1-ethyl-3-(3-
dimethylaminopropyl) carbodiimide; NBS, N-bromosuccinimide; HOBt, 1-hydroxybenzotriazole; DMF,
N,N-dimethylformamide; PK, pharmacokinetic
References and notes
1.
2.
3.
World Health Organization. Global Tuberculosis Report 2015; WHO/HTM/TB/2016.23
World Health Organization. Treatment of tuberculosis: guidelines 2010; WHO/HTM/TB/2009.420
Centers for Disease Control and Prevention. Emergence of Mycobacterium tuberculosis with
Extensive Resistance to Second-Line Drugs — Worldwide, 2000–2004 MMWR Weekly. 2006, 55
(11), 301–305.
4.
Cox E.; Laessig K. N Engl J Med. 2014, 371(8), 689-691